This invention relates to a transmission type projection screen apparatus and relates in particular to a multi-screen apparatus in which plural transmission screen units are closely arranged in horizontal and/or vertical directions in combination with plural projectors so as to constitute a large projection screen system.
FIG. 7 shows a conventional transmission type projection screen having a circular Fresnel lens 11a and a lenticular lens 12a at its opposite sides, which are made essentially of a transparent synthetic resin such as acrylic resin, vinyl chloride resin, styrene, resin, polycarbonate resin, acrylonitrile-styrene copolymerized resin or the like as one body. Since relative positions of the lenses 11a, 12a can be precisely maintained, such a projection screen has been used in practice. However, it is difficult to manufacture a large size screen.
FIG. 8 shows another conventional projection screen composed of two sheets such as a combination of a Fresnel lens sheet 11b and a lenticular lens sheet 12b which are separately made of one of the above-stated synthetic resins and adhered to each other. Since a broad Fresnel lens sheet cannot be manufactured, it cannot be practically used in case of a large screen.
It has been recently proposed to produce a large multi-screen apparatus composed of many small transmission screen units which are supported by an aluminum sash frame and plural supports. However, the supports appear as relatively wide seams on the multi-screen, which reduces commercial values.